This invention generally relates to preventative maintenance apparatus and methods in semiconductor processing and more particularly to a cleaning container and method for cleaning thermocouple sleeves used in LP furnaces.
In semiconductor fabrication, various layers of insulating material, semiconducting material and conducting material are formed to produce a multilayer semiconductor device. The layers are patterned to create features that taken together, form elements such as transistors, capacitors, and resistors. These elements are then interconnected to achieve a desired electrical function, thereby producing an integrated circuit (IC) device. The formation and patterning of the various device layers are achieved using conventional fabrication techniques, such as oxidation, implantation, deposition, epitaxial growth of silicon, lithography, etching, and planarization.
In the semiconductor processing art there are several processes that require a thermal treatment at an elevated temperature under controlled ambient conditions. For example, low pressure (LP) furnaces that are capable of treating a batch of semiconductor wafers are used extensively including for example, to accelerate diffusion processes following implantation of a doping material in a semiconductor, for example, silicon semiconductor wafer. Other exemplary processes include high temperature oxidations (HTO), low temperature oxidations (LTO), and film-formation processing called low pressure chemical vapor deposition (LPCVD) for forming for example, metal nitride films and silicon oxide films derived from TEOS.
To accomplish such thermal treatments, for example, a vertically oriented LP furnace is frequently used for subjecting a batch of semiconductor wafers (process wafers) to a thermal treatment. The vertically oriented LP furnace is generally configured such that a quartz wafer boat holding wafers in multiple layers is conveyed into a vertical reaction vessel, usually from below, a lower aperture of the reaction vessel being closed hermetically by a lid member that supports the wafer boat.
For example, referring to FIG. 1A is shown a cross sectional representation shown of a portion of a vertically oriented LP furnace 10 with quartz wafer boat 12 having a cassette portion 12B for holding a plurality of wafers. Surrounding the wafer boat 12 is a cylindrical inner tube 14, for example, quartz that is ambiently sealed at the bottom portion of outer tube 16, again typically formed of quartz. Disposed in the annular space 20 between outer tube 16 and inner tube 14 is typically at least one thermocouple (TC) quartz sleeve e.g., 18, for holding a thermocouple wire junction to sense the temperature at the peripheral portion of the LP furnace. Quartz is a highly preferred material for forming furnace parts such as the wafer boat 12, the inner tube 14, outer tube 16, and TC sleeve 18. Quartz is a crystalline material with a high degree of purity and a high melting temperature thereby able to withstand thermal treatments while avoiding contamination of the process wafers. A lid member 22 supports the wafer boat 12 and typically is equipped with an O-ring for providing a hermetic seal. In operation, the wafer boat 12 holding a plurality of process wafers in cassette 12B is conveyed upward through a lower aperture 26 of the manifold 28 with lid member 22 forming a hermetic seal with manifold 28.
As a result of the critical need for a clean processing environment in semiconductor wafer processing, including the quartz furnace parts, for example, the wafer boat 12, the inner tube 14, outer tube 16, and TC sleeve 18, frequent shut down of the LP furnace operation is required to clean the quartz furnace parts as they tend to rapidly accumulate impurities from the various processing operations. In a typical semiconductor processing operation, several LP furnaces are in operation with the corresponding result that several may be shut down at one time for parallel preventive maintenance (PM) to improve the process wafer throughput and therefore the efficiency of the operation.
In a typical cleaning or PM operation where the quartz parts are cleaned a typical process flow chart is shown in FIG. 1B including one or more chemical solvent cleaning (soak) steps 102, using, for example hydrogen fluoride (HF) and optionally, a second chemical solvent for a total of for about 1 to about 3 hours. The chemical solvent treatment is followed by a deionized water (DIW) soak 104 for about 3 hours, a vertical DIW rinse 106 for about 1.5 hours, and a baking step 108 for about 2 hours for a total PM time period of about 7 to about 10 hours depending in part on the particular processes the LP furnace is dedicated to.
In a typical PM operation, the LP furnace parts are disassembled in the sequential order of removing the wafer boat 12, the inner tube 14, the TC sleeve 18, and the outer tube 16. The LP furnace parts are then subjected to a cleaning procedure carried out, preferably, in parallel according to the steps discussed. Following the cleaning procedure, the LP furnace parts are assembled in the sequential order of the outer tube, 16, the TC sleeve e.g., 18, the inner tube 14, and the wafer boat 12.
One problem with the prior art cleaning procedure is the cleaning process for the TC sleeves e.g., 18. According to the prior art cleaning process, only a limited number, for example two, TC sleeves are cleaned at a time due to the method used to protect the thermocouple wires from corrosive attack by the chemical cleaning solvent used, for example, HF. For example, the TC quartz sleeves including the TC wire and trailing TC wire extending through the sealed quartz sleeves are typically supported on a fork like fixture for automated dipping through the various cleaning steps. As a result, the trailing TC wire must be maintained above the level of the cleaning solvent, for example, tied to the fork like fixture via a cable tie, presenting the potential problems of loosening of the trailing TC to contact the cleaning solvent or contacting the cleaning solvent due to a high level of cleaning solvent contained in a container for dipping the TC sleeves. Furthermore, the due to the order of assembly, the limited number of TC sleeves that may be cleaned at one time creates a bottleneck effect, reducing overall throughput and efficiency.
There is therefore a need in the semiconductor processing art to develop an improved apparatus and method for cleaning the quartz TC sleeves to allow for a greater number of TC sleeves to be cleaned at one time without the danger of cleaning solvent attack of the associated TC wires.
It is therefore an object of the invention to provide an improved apparatus and method for cleaning the quartz TC sleeves to allow for a greater number of TC sleeves to be cleaned at one time without the danger of cleaning solvent attack of the associated TC wires while overcoming other shortcomings and deficiencies in the prior art.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a cleaning container for chemically cleaning elongated members.
In a first embodiment of the cleaning container, the cleaning container includes a first body member and a second body member said first body member and second body member respectively forming a first containing space and a second containing space including a first means for reversibly compressively sealing the first body member and the second body member to a form a combined containing space for sealably holding a cleaning solution level; a cap member disposed at a distal end of the first body member said cap member including a second means for reversibly compressively sealing a first opening in communication with the first containing space; and, a second opening centrally disposed in a distal end of the second containing space said second opening including a third means for reversibly compressively sealing around at least one elongated member penetrating through said second opening.
In related embodiments, the combined containing space forms a sealably closed hollow cylindrical shape. Further, the first, second and third means for reversibly compressively sealing include at least one of a threading means and a clamping means. Further, the threading means and the clamping means include a means for deformably compressing an O-ring to form a liquid tight seal. Further yet, an axial dimension of the sealably closed hollow cylindrical shape is greater than a radial dimension. Yet further, the axial dimension is sufficient to accommodate a length of the at least one elongated member to include at least one thermocouple sleeve.
In another embodiment, the second opening is a cylindrical opening of sufficient diameter to accommodate at one time a plurality of the at least one elongated member including about 6 to about 10 thermocouple sleeves.
In a further related embodiment, the third means for reversibly compressively sealing includes an inner compression sleeve and an outer compression sleeve for deformably compressing an O-ring to seal around the at least one elongated member to include at least one thermocouple sleeve.
In another embodiment, the at least one elongated member includes at least one thermocouple sleeve including a plurality thermocouple wires extending from the at least one thermocouple sleeve. Further, the cleaning solution level covers a height of the at least one elongated member to include at least one thermocouple sleeve.
In another embodiment, at least the combined containing space is formed of a chemically resistant material including a resistance to hydrofluoric acid (HF).
The present invention further provides a method for cleaning thermocouple sleeves including providing a plurality of thermocouple sleeves including a plurality of trailing thermocouple wires for cleaning; providing a cleaning container including at least a first sealing means such that at least a portion of each of the plurality of thermocouple sleeves sealably penetrates through the cleaning container to contact a cleaning solution contained in said cleaning container; and, sealably penetrating the cleaning container with the plurality of thermocouple sleeves to form a plurality of sealably penetrating portions of the plurality of thermocouple sleeves; and providing the cleaning solution contained in the cleaning container to clean the plurality of thermocouple sleeves.
In related embodiments, the step of sealably penetrating includes the at least a first sealing means forming a liquid tight seal around the plurality of trailing thermocouple wires. Further, the cleaning container includes a second sealing means whereby the cleaning container may be separated into 2 containing parts said second sealing means forming a liquid tight seal at a mating interface of the 2 containing parts. Further yet, at least one of the 2 containing parts is sized to contain a cleaning solution level for covering the plurality of the sealably penetrating portions.
In another embodiment, the plurality of thermocouple sleeves includes a plurality of from about 4 to about 10.
In other related embodiments, the cleaning solution includes at least hydrofluoric acid (HF). Further, at least a containing portion of the cleaning container includes a corrosion resistant material including a resistance to hydrofluoric acid (HF). Further yet, the corrosion resistant material includes at least one of polyethylene and polypropylene.
In another embodiment, the cleaning container includes a sealable cap at an end of the container distal from the at least a first sealing means for adding and removing a cleaning solution.
These and other embodiments, aspects and features of the invention will be better understood from a detailed description of the preferred embodiments of the invention which are further described below in conjunction with the accompanying Figures.